The instant invention relates to the stabilization of a wide variety of ambient cured coating compositions by the incorporation therein of Np--OR.sub.1 -substituted hindered amine light stabilizers.
Hindered amine light stabilizers are well known to be effective in stabilizing a host of organic substrates including polymers against the deleterious effects of oxygen and light. Such hindered amine light stabilizers have been used in the stabilization of hot-crosslinkable alkyd or acrylic metallic stoving lacquers (U.S. Pat. No. 4,426,472) and in stabilizing acid-catalyzed stoving lacquers based on hot-crosslinkable acrylic polyester or alkyd resins (U.S. Pat. Nos. 4,344,876 and 4,426,471). The hindered amine light stabilizers of these patents do not possess structures having an O-substituted hydroxyl group substituted directly on the hindered N-atom of the compound.
Related hindered amine stabilizers have been utilized individually and in combination with ultra-violet light absorbers to improve the performance characteristics of ambient cured coating systems. Notwithstanding such improvements, there still exists a need to further retard the photooxidation and photodegradation of such ambient cured systems and thereby provide increased effectiveness by maintaining the physical integrity of the coatings. Such effectiveness can be manifested by prevention of embrittlement, cracking, corrosion, erosion, loss of gloss, chalking and yellowing of the coating.
It has now been determined that the aforementioned improvements can be achieved by substitution on the hindered N-atom of the hindered amines with OR.sub.1 groups and the utilization of such derivatives in ambient cured coating systems. In particular, the physical integrity of the coatings is maintained to a higher degree with significant reduction in loss of gloss and yellowing. Accordingly, the present invention relates to the use of N--OR.sub.1 -substituted 2,2,6,6-tetraalkylpiperidine compounds, optionally together with further stabilizers, for stabilizing ambient cured coatings based on alkyd resins; thermoplastic acrylic resins; acrylic alkyds; acrylic alkyd or polyester resins optionally modified with silicon, isocyanates, isocyanurates, ketimines or oxazolidines; and epoxide resins crosslinked with carboxylic acids, anhydrides, polyamines or mercaptans; and acrylic and polyester resin systems modified with reactive groups in the backbone thereof and crosslinked with epoxides; against the degradative effects of light, moisture and oxygen.
The N--OR.sub.1 - substituted hindered amine compounds of this invention contain the group ##STR1## wherein R is hydrogen or methyl, and R.sub.1 is C.sub.1 -C.sub.18 alkyl, C.sub.2 -C.sub.18 alkenyl, C.sub.2 -C.sub.18 alkynyl, C.sub.5 --C.sub.7 cycloalkyl, C.sub.6 -C.sub.10 bicycloalkyl, C.sub.5 -C.sub.8 cycloalkenyl, C.sub.6 -C.sub.10 aryl, C.sub.7 -C.sub.9 aralkyl, C.sub.7 -C.sub.9 aralkyl substituted by alkyl or aryl, or ##STR2## wherein D is C.sub.1 -C.sub.18 alkyl, C.sub.1 -C.sub.18 alkoxy, phenyl, phenyl substituted by hydroxy, alkyl or alkoxy, or amino or amino mono- or disubstituted by alkyl or phenyl. Some are known compounds while others are claimed in copending applications Ser. Nos. 99,414 and 99,419.
More particularly, the instant invention relates to the use of a derivative having one of formulae A to P ##STR3## wherein
R is hydrogen or methyl,
R.sub.1 is independently C.sub.1 -C.sub.18 alkyl, C.sub.2 -C.sub.18 alkenyl, C.sub.2 -C.sub.18 alkynyl, C.sub.5 -C.sub.12 cycloalkyl, C.sub.6 -C.sub.10 bicycloalkyl, C.sub.5 -C.sub.8 cycloalkenyl, C.sub.6 -C.sub.10 aryl, C.sub.7 -C.sub.9 aralkyl, C.sub.7 -C.sub.9 aralkyl substituted by alkyl or aryl, or ##STR4## wherein D is C.sub.1 -C.sub.18 alkyl, C.sub.1 -C.sub.18 alkoxy, phenyl, phenyl substituted by hydroxy, alkyl or alkoxy, or amino or amino mono- or disubstituted by alkyl or phenyl;
m is 1-4,
when m is 1,
R.sub.2 is hydrogen, C.sub.1 -C.sub.18 alkyl optionally interrupted by one or more oxygen atoms, C.sub.2 -C.sub.12 alkenyl, C.sub.6 -C.sub.10 aryl, C.sub.7 -C.sub.18 aralkyl, glycidyl, a monovalent acyl radical of an aliphatic, cycloaliphatic, araliphatic or aromatic carboxylic acid, or of a carbamic acid, preferably an acyl radical of an aliphatic carboxylic acid having 2-18 C atoms, of a cycloaliphatic carboxylic acid having 5-12 C atoms or of an aromatic carboxylic acid have 7-15 C atoms, or ##STR5## wherein x is 0 is 1, or ##STR6## wherein y is 2-4;
when m is 2,
R.sub.2 is C.sub.1 -C.sub.12 alkylene, C.sub.4 -C.sub.12 alkenylene, xylylene, a divalent acyl radical of an aliphatic, cycloaliphatic, araliphatic or aromatic dicarboxylic acid or of a dicarbamic acid, preferably an acyl radical of an aliphatic dicarboxylic acid having 2-18 C atoms, of a cycloaliphatic or aromatic dicarboxylic acid having 8-14 C atoms, or of an aliphatic, cycloaliphatic or aromatic dicarbamic acid having 8-14 C atoms; ##STR7## wherein D.sub.1 and D.sub.2 are independently hydrogen, an alkyl radical containing up to 8 carbon atoms, an aryl or aralkyl radical including 3,5-di-t-butyl-4-hydroxybenzyl radical, D.sub.3 is hydrogen, or an alkyl or alkenyl radical containing up to 18 carbon atoms, and d is 0-20;
when m is 3, R.sub.2 is a trivalent acyl radical of an aliphatic, unsaturated aliphatic, cycloaliphatic, or aromatic tricarboxylic acid;
when m is 4, R.sub.2 is a tetravalent acyl radical of a saturated or unsaturated aliphatic or aromatic tetracarboxylic acid including 1,2,3,4-butanetetracarboxylic acid, 1,2,3,4-but-2-enetetracarboxylic acid, and 1,2,3,5- and 1,2,4,5-pentanetetracarboxylic acid;
is 1, 2 or 3,
R.sub.3 is hydrogen, C.sub.1 -C.sub.12 alkyl, C.sub.5 -C.sub.7 cycloalkyl, C.sub.7 -C.sub.9 aralkyl, C.sub.2 -C.sub.18 alkanoyl, C.sub.3 -C.sub.5 alkenoyl or benzoyl;
when p is 1,
R.sub.4 is hydrogen, C.sub.1 -C.sub.18 alkyl, C.sub.5 -C.sub.7 cycloalkyl, C.sub.2 -C.sub.8 alkenyl unsubstituted or substituted by a cyano, carbonyl or carbamide group, aryl, aralkyl, or it is glycidyl, a group of the formula --CH.sub.2 --CH(OH)--Z or of the formula --CO--Z or --CONH--Z wherein Z is hydrogen, methyl or phenyl; or a group of the formulae ##STR8## or R.sub.3 and R.sub.4 together when p is 1 can be alkylene of 4 to 6 carbon atoms or 2-oxo-polyalkylene or the cyclic acyl radical of an aliphatic or aromatic 1,2- or 1,3-dicarboxylic acid,
when p is 2,
R.sub.4 is a direct bond or is C.sub.1 -C.sub.12 alkylene, C.sub.6 -C.sub.12 arylene, xylylene, a --CH.sub.2 CH(OH)--CH.sub.2 group, or a group --CH.sub.2 --CH(OH)--CH.sub.2 --O--X--O--CH.sub.2 --CH(OH)--CH.sub.2 -- wherein X is C.sub.2 -C.sub.10 alkylene, C.sub.6 -C.sub.15 arylene or C.sub.6 -C.sub.12 cycloalkylene; or, provided that R.sub.3 is not alkanoyl, alkenoyl or benzoyl, R.sub.4 can also be a divalent acyl radical of an aliphatic, cycloaliphatic or aromatic dicarboxylic acid or dicarbamic acid, or can be the group --CO--; or R.sub.4 is ##STR9## where T.sub.8 and T.sub.9 are independently hydrogen, alkyl of 1 to 18 carbon atoms, or T.sub.8 and T.sub.9 together are alkylene of 4 to 6 carbon atoms or 3-oxapentamethylene, preferably T.sub.8 and T.sub.9 together are 3-oxapentamethylene;
when p is 3,
R.sub.4 is 2,4,6-triazinyl,
n is 1 or 2,
when n is 1,
R.sub.5 and R'.sub.5 are independently C.sub.1 -C.sub.12 alkyl, C.sub.2 -C.sub.12 alkenyl, C.sub.7 -C.sub.12 aralkyl, or R.sub.5 is also hydrogen, or R.sub.5 and R'.sub.5 together are C.sub.2 -C.sub.8 alkylene or hydroxyalkylene or C.sub.4 -C.sub.22 acyloxyalkylene;
when n is 2,
R.sub.5 and R'.sub.5 together are (--CH.sub.2).sub.2 C(CH.sub.2 --).sub.2 ;
R.sub.6 is hydrogen, C.sub.1 -C.sub.12 alkyl, allyl, benzyl, glycidyl or C.sub.2 -C.sub.6 alkoxyalkyl;
when n is 1,
R.sub.7 is hydrogen, C.sub.1 -C.sub.12 alkyl, C.sub.3 -C.sub.5 alkenyl, C.sub.7 -C.sub.9 aralkyl, C.sub.5 -C.sub.7 cycloalkyl, C.sub.2 -C.sub.4 hydroxyalkyl, C.sub.2 -C.sub.6 alkoxyalkyl, C.sub.6 -C.sub.10 aryl, glycidyl, a group of the formula --(CH.sub.2)t--COO--Q or of the formula --(CH.sub.2).sub.t --O--CO--Q wherein t is 1 or 2, and Q is C.sub.1 -C.sub.4 alkyl or phenyl; or
when n is 2,
R.sub.7 is C.sub.2 -C.sub.12 alkylene, C.sub.6 -C.sub.12 arylene, a group --CH.sub.2 CH(OH)--CH.sub.2 --O--X--O--CH.sub.2 --CH(OH)--CH.sub.2 -- wherein X is C.sub.2 -C.sub.10 alkylene, C.sub.6 -C.sub.15 arylene or C.sub.6 -C.sub.12 cycloalkylene, or a group --CH.sub.2 CH(OCH.sub.2 --CH(OZ')CH.sub.2).sub.2 -- wherein Z' is hydrogen, C.sub.1 -C.sub.18 alkyl, allyl, benzyl, C.sub.2 -C.sub.12 alkanoyl or benzoyl;
Q.sub.1 is --N(R.sub.8)-- or --O--; E is C.sub.1 -C.sub.3 alkylene, the group --CH.sub.2 --CH(R.sub.9)--O--wherein R.sub.9 is hydrogen, methyl or phenyl, the group --(CH.sub.2).sub.3 --NH-- or a direct bond;
R.sub.10 is hydrogen or C.sub.1 -C.sub.18 alkyl, R.sub.8 is hydrogen, C.sub.1 -C.sub.18 alkyl, C.sub.5 -C.sub.7 cycloalkyl, C.sub.7 -C.sub.12 aralkyl, cyanoethyl, C.sub.6 -C.sub.10 aryl, the group --CH.sub.2 --CH(R.sub.9)--OH wherein R.sub.9 has the meaning defined above; a group of the formula ##STR10## or a group of the formula ##STR11## wherein G is C.sub.2 -C.sub.6 alkylene or C.sub.6 -C.sub.12 arylene; or R.sub.8 is a group --E--CO--NH--CH.sub.2 --OR.sub.10 ;
Formula F denotes a recurring structural unit of a polymer where T.sub.3 is ethylene or 1,2-propylene, or is the repeating structural unit derived from an alpha-olefin copolymer with an alkyl acrylate or methacrylate; preferably a copolymer of ethylene and ethyl acrylate, and where k is 2 to 100;
T.sub.4 has the same meaning as R.sub.4 when p is 1 or 2,
T.sub.5 is methyl,
T.sub.6 is methyl or ethyl, or T.sub.5 and T.sub.6 together are tetramethylene or pentamethylene, preferably T.sub.5 and T.sub.6 are each methyl,
M and Y are independently methylene or carbonyl preferably M is methylene and Y is carbonyl, and T.sub.4 is ethylene where n is 2;
T.sub.7 is the same as R.sub.7, and T.sub.7 is preferably octamethylene where n is 2,
T.sub.10 and T.sub.11 are independently alkylene of 2 to 12 carbon atoms, or T.sub.11 is ##STR12##
T.sub.12 is piperazinyl,
--NR.sub.11 --(CH.sub.2).sub.d --NR.sub.11 -- or ##STR13## where R.sub.11 is the same as R.sub.3 or is also ##STR14##
a, b and c are independently 2 or 3, and f is 0 or 1, preferably a and c are each 3, b is 2 and f is 1; and
e is 2, 3 or 4, preferably 4;
T.sub.13 is the same as R.sub.2 with the proviso that T.sub.13 cannot be hydrogen when n is 1;
E.sub.1 and E.sub.2, being different, each are --CO-- or --N(E.sub.5)where E.sub.5 is hydrogen, C.sub.1 -C.sub.12 alkyl or C.sub.4 -C.sub.22 alkoxycarbonylalkyl, preferably E.sub.1 is --CO-- and
E.sub.3 is hydrogen, alkyl of 1 to 30 carbon atoms, phenyl, naphthyl, said phenyl or said naphthyl substituted by chlorine or by alkyl of 1 to 4 carbon atoms, or phenylalkyl of 7 to 12 carbon atoms, or said phenylalkyl substituted by alkyl of 1 to 4 carbon atoms,
E.sub.4 is hydrogen, alkyl of 1 to 30 carbon atoms, phenyl, naphthyl or phenylalkyl of 7 to 12 carbon atoms, or
E.sub.3 and E.sub.4 together are polymethylene of 4 to 17 carbon atoms, or said polymethylene substituted by up to four alkyl groups of 1 to 4 carbon atoms, preferably methyl,
R.sub.2 of formula (N) is a previously defined when m is 1, G.sub.1 is a direct bond, C.sub.1 -C.sub.12 alkylene, phenylene or --NH--G'--NH wherein G' is C.sub.1 -C.sub.12 alkylene, and
E.sub.6 is an aliphatic or aromatic tetravalent radical.
In the structures A to P, if any substituents are C.sub.1 -C.sub.18 alkyl, they are for example methyl, ethyl, n-propyl, n-butyl, sec-butyl, tert-butyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-hexadecyl or n-octadecyl. Typical cycloalkyl groups include cyclopentyl, cyclohexyl and cyclododecyl; typical cycloalkenyl groups include cyclohexenyl; while typical aralkyl groups include benzyl, alpha-methylbenzyl, alpha,alpha-dimethylbenzyl or phenethyl. C.sub.1 -C.sub.12 alkyl and cyclohexyl are preferred.
If R.sub.2 is a monovalent acyl radical of a carboxylic acid, it is for example an acyl radical of acetic acid, stearic acid, salicylic acid, benzoic acid or .beta.-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid.
If R.sub.2 is a divalent acyl radical of a dicarboxylic acid, it is for example an acyl radical of oxalic acid, adipic acid, succinic acid, suberic acid, sebacic acid, phthalic acid dibutylmalonic acid, dibenzylmalonic acid or butyl-(3,5-di-tert-butyl-4-hydroxybenzyl)-malonic acid, or bicycloheptenedicarboxylic acid, with succinates, sebacates, phthalates and isophthalates being preferred.
If R.sub.2 is a divalent acyl radical of a dicarbamic acid, it is for example an acyl radical of hexamethylenedicarbamic acid or of 2,4-toluylenedicarbamic acid.
The following compounds are examples of polyalkylpiperidine starting materials useful in making the hydroxylamine derivatives of formula A.
4-benzyloxy-2,2,6,6-tetramethylpiperidine PA0 4-acryloyloxy-2,2,6,6-tetramethylpiperidine PA0 4-hydroxy-2,2,6,6-tetramethylpiperidine PA0 4-stearoyloxy-2,2,6,6-tetramethylpiperidine PA0 di-(2,2,6,6-tetramethylpiperidin-4-yl) adipate PA0 di-(2,2,6,6-tetramethylpiperidin-4-yl) sebacate PA0 di-(2,2,6,6-tetramethylpiperidin-4-yl)phthalate PA0 alpha,alpha'-(di-2,2,6,6-tetramethyl PA0 piperidine-4-oxy)-p-xylene PA0 di-(2,2,6,6-tetramethylpiperidin-4-yl)succinate PA0 di-(2,2,6,6-tetramethylpiperidin-4-yl)malonate PA0 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine PA0 1-acetoxy-4-hydroxy-2,2,6,6-tetramethylpiperidine PA0 (2,2,6,6-tetramethylpiperidin-4-yl)-[4-(2-oxoazepin-1-yl)-2,2,6,6-tetrameth ylpiperidin-4-yl]acetate. PA0 N,N'-bis(2,2,6,6-tetramethylpiperidin-4-yl)-hexamethylene-1,6-diamine, PA0 N,N'-bis-(2,2,6,6-tetramethylpiperidin-4-yl)-hexamethylene-1,6-diacetamide, PA0 4-benzylamino-2,2,6,6-tetramethylpiperidine, PA0 N-n-butyl--N-(2,2,6,6-tetramethylpiperidin-4-yl)-4-hydroxy-3,5-di-tert.buty l benzamide, PA0 N,N'-bis-(2,2,6,6-tetramethylpiperidin-4-yl)--N,N'-di-butyl-adipamide, PA0 N,N'-bis-(2,2,6,6-tetramethylpiperidin-4-yl)--N,N'-dicyclohexyl-(2-hydroxyp ropylene-diamine), PA0 N,N'-bis-(2,2,6,6-tetramethylpiperidin-4-yl)-p-xylylenediamine, PA0 4-(3-methyl-4-hydroxy-5-tert-butyl-benzoyl acetamido)-2,2,6,6-tetramethylpiperidine, PA0 alpha-cyano-.beta.-methyl-.beta.-[N-(2,2,6,6-tetramethylpiperidin-4-yl]-ami no-acrylic acid methyl ester PA0 1-acetoxy--N-butylamino-2,2,6,6-tetramethylpiperidine PA0 1-oxyl-2,2,6,6-tetramethylpiperidin-4-one PA0 9-aza-8,8,10,10-tetramethyl-1,5-dioxaspiro[5.5]undecane, PA0 9-aza-8,8,10,10-tetramethyl-3-ethyl-1,5-dioxaspiro[5.5]undecane, PA0 2,2,6,6-tetramethylpiperidine-4-spiro-2'-(1',3'-dioxane)-5'-spiro-5"-(1",3" -dioxane)-2"-spiro-4"'-(2"',2"'-6"',6"'-tetramethylpiperidine). PA0 3-benzyl-1,3,8-triaza-7,7,9,9-tetramethylspiro[4.5]decane-2,4-dione, PA0 3-n-octyl-1,3,8-triaza-7,7,9,9-tetramethylspiro[4.5]decane-2,4-dione, PA0 3-allyl-1,3,8-triaza-1,7,7,9,9-pentamethylspiro[4.5]decane-2,4-dione, PA0 N-hydroxymethyl--N'-2,2,6,6-tetramethylpiperidin-4-yl urea, PA0 N-methoxymethyl--N'-2,2,6,6-tetramethylpiperidin-4-yl urea, PA0 N-methoxymethyl--N'-n-dodecyl--N'-2,2,6,6-tetramethylpiperidin-4-yl-urea, and PA0 O-(2,2,6,6-tetramethylpiperidin-4-yl)--N-methoxymethylurethane. PA0 poly-{[6-[(1,1,3,3-tetramethylbutyl)-imino]-1,3,5-triazine-2,4-diyl][2-(1-o xyl-2,2,6,6-tetramethyl piperidyl)-imino]-hexamethylene-4[4-(1-oxyl-2,2,6,6-tetramethylpiperidyl]- imino]}, PA0 2,3,9,10-perylene tetracarboxylic acid dianhydride PA0 1,4,5,8-naphthalene tetracarboxylic acid dianhydride PA0 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic acid dianhydride PA0 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic acid dianhydride PA0 2,3,6,7-tetrachloronaphthalene-1,4,5,8-tetracarboxylic acid dianhydride PA0 phenanthrene-1,8,9,10-tetracarboxylic acid dianhydride PA0 2,3,3',4'-benzophenonetetracarboxylic acid dianhydride PA0 pyromellitic dianhydride PA0 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride PA0 2,2',3,3,-benzophenonetetracarboxylic acid dianhydride PA0 3,3',4,4'-biphenyltetracarboxylic acid dianhydride PA0 2,2',3,3'-biphenyltetracarboxylic acid dianhydride PA0 4,4'-isopropylidenediphthalic anhydride PA0 3,3'-isopropylidenediphthalic anhydride PA0 4,4'-oxydiphthalic anhydride PA0 4,4'-sulfonyldiphthalic anhydride PA0 3,3'-oxydiphthalic anhydride PA0 4,4'-methylenediphthalic anhydride PA0 4,4'-thiodiphthalic anhydride PA0 4,4'-ethylidenediphthalic anhydride PA0 2,3,6,7-naphthalenetetracarboxylic acid dianhydride PA0 1,2,4,5-naphthalenetetracarboxylic acid dianhydride PA0 1,2,5,6-naphthalenetetracarboxylic acid dianhydride PA0 benzene-1,2,3,4-tetracarboxylic acid dianhydride PA0 pyrazine-2,3,5,6-tetracarboxylic acid dianhydride. PA0 1. di-(1-acetoxy-2,2,6,6-tetramethylpiperidin-4-yl)phthalate PA0 2. di-(1-acetoxy-2,2,6,6-tetramethylpiperidin-4-yl)isophthalate PA0 3. di-(1-acetoxy-2,2,6,6-tetramethylpiperidin-4-yl) sebacate PA0 4. di-(1-acetoxy-2,2,6,6-tetramethylpiperidin-4-yl) succinate PA0 5. di-(1-acetoxy-2,2,6,6-tetramethylpiperidin-4-yl) adipate PA0 6. di-(1-acetoxy-2,2,6,6-tetramethylpiperidin-4-yl) n-butylmalonate PA0 7. di-(1-acetoxy-2,2,6,6-tetramethylpiperidin-4-yl) 2,2-diethylmalonate PA0 8. poly-[6-[(1,1,3,3-tetramethylbutyl)-imino]-1,3,5-triazine-2,4-diyl][2-(1-a cetoxy-2,2,6,6-tetramethylpiperidyl)-imino]-hexamethylene-[4-(1-acetoxy-2,2 ,6,6-tetramethylpiperidyl)-imino] PA0 9. 1,4-diacetoxy-2,2,6,6-tetramethylpiperidine PA0 10. 1-acetoxy-4-hydroxy-2,2,6,6-tetramethylpiperidine PA0 11. di-(1-propionoxy-2,2,6,6-tetramethylpiperidin-4-yl)adipate PA0 12. di-(4-benzoyloxy-2,2,6,6-tetramethylpiperidin-4-yl)oxalate PA0 13. (1-acetoxy-2,2,6,6-tetramethylpiperidin-4-yl)-4-hydroxy-3,5-di-tert.butylb enzoate PA0 14. 2-(4-hydroxy-3,5-di-tert.butylbenzyl)-2-(1-acetoxy-2,2,6,6-tetramethylpipe ridin-4-yl) n-butylmalonate PA0 15. N-(1-acetoxy-2,2,6,6-tetramethylpiperidin-4-yl)N-(n-butyl)-4-(4-hydroxy-3, 5-di-tert.butylbenzoyloxy)-3,5-di-tert.butylbenzamide PA0 16. 1,6-di-(N-acetyl--N-(1-acetoxy-2,2,6,6-tetramethylpiperidin-4-yl)]aminohex ane PA0 17. di-(1-acetoxy-2,2,6,6-tetramethylpiperidin-4-yloxy)hexane-1,6-dicarbamate PA0 18. 1-acetoxy-4-(N-acetyl--N-n-dodecylamino)-2,2,6,6-tetramethylpiperidine PA0 19. di-(1-propionoxy-2,2,6,6-tetramethylpiperidin-4-yl)succinate PA0 20. di-(4-n-octadecanoyloxy-2,2,6,6-tetramethylpiperazin-1-yl)oxalate PA0 21. 1,4-di-(2-ethylhexanoyloxy)-2,2,6,6-tetramethylpiperidine PA0 22 di-(1-benzoyloxy-2,2,6,6-tetramethylpiperidin-4-yl) sebacate PA0 23. 1-benzoyloxy-4-(N-n-butyl--N-benzoylamino)-2,2,6,6-tetramethylpiperidine PA0 24. 1-(1-benzoyloxy-2,2,6,6-tetramethylpiperdin-4-yl)azepin-2-one PA0 25. 1-benzoyloxy-1'-benzyloxy-di-(2,2,6,6-tetramethylpiperidin-4-yl)]isophthal ate PA0 26. 1,4-di-(4-hydroxy-3,5-di-tert-butylbenzoyloxy)-2,2,6,6-tetramethylpiperidi ne PA0 27. n-butyl-(4-benzoyloxy-2,2,6,6-tetramethylpiperidin-4-yl)carbonate PA0 28. 1-carbamoyloxy-4-benzoyloxy-2,2,6,6-tetramethylpiperidine PA0 29 di(1-carbamoyloxy-2,2,6,6-tetramethylpiperidin-4-yl)sebacate PA0 30. di-(1-n-butylcarbamoyloxy-2,2,6,6-tetramethylpiperidin-4-yl)2,2-diethylmal onate PA0 31. di-(4-benzoyloxy-2,2,6,6-tetramethylpiperidin-1-yl)-2,4,4-trimethylhexane- 1,6-dicarbamate PA0 32. alpha,alpha'-(di-1-ethoxy-2,2,6,6-tetramethylpiperidin-4-yloxy)-p-xylene PA0 33. 4-benzyloxy-1-ethoxy-2,2,6,6-tetramethylpiperidine PA0 34. 1,4-dibenzyloxy-2,2,6,6-tetramethylpiperidine PA0 35. alpha,alpha'-(di-1-benzyloxy-2,2,6,6-tetramethylpiperidin-4-yloxy)-p-xylen e PA0 36. di-(1-benzyloxy-2,2,6,6-tetramethylpiperidin-4-yl)sebacate PA0 37. 4-benzoyloxy-1-(alpha-methylbenzyloxy)-2,2,6,6-tetramethylpiperidine PA0 38. di-[1-(alpha-methylbenzyloxy)-2,2,6,6-tetramethylpiperidin-4-yl]sebacate PA0 39. 1,4-dimethoxy-2,2,6,6-tetramethylpiperidine PA0 40. 4-benzoyloxy-1-methoxy-2,2,6,6-tetramethylpiperidine PA0 41. di-(1-methoxy-2,2,6,6-tetramethylpiperidin-4-yl) sebacate PA0 42. di-(1-methoxy-2,2,6,6-tetramethylpiperidin-4-yl)succinate PA0 43. (1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl)-3,5-di.-t.butyl-4-hydr oxybenzoate PA0 44. 1-cyclohexyloxy-4-octadecanoyloxy-2,2,6,6-tetramethylpiperidine PA0 45. di-(1-methoxy-2,2,6,6-tetramethylpiperidin-4-yl)isophthalate PA0 46. di-(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl)sebacate PA0 47. di-(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl)isophthalate PA0 48. di-(1-heptyloxy-2,2,6,6-tetramethylpiperidin-4-yl)sebacate PA0 49. di-[1-(alpha-methylbenzyloxy)-2,2,6,6-tetramethylpiperidin-4-yl]terephthal ate PA0 50. di-(1-ethoxy-2,2,6,6-tetramethylpiperidin-4-yl)sebacate PA0 51. di-(1-cumyloxy-2,2,6,6-tetramethylpiperidin-4-yl)sebacate PA0 52. 3,15-di-alpha-methylbenzyloxy-2,2,4,4,14,14,16,16-octamethyl-7,11,18,21-te traoxa-3,15-diazatrispiro[5.2.2.5.2.2]heneicosane PA0 53. 3,15-dicyclohexyloxy-2,2,4,4,14,14,16,16-octamethyl-7,11,18,21-tetraoxa-3, 15-diazatrispiro[5.2.2.5.2.2]heneicosane PA0 54. di-(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl)succinate PA0 55. di-[1-(alpha-methylbenzyloxy)-2,2,6,6-tetramethylpiperidin-4-yl]succinate PA0 56. di-(1-nonyloxy-2,2,6,6-tetramethylpiperidin-4-yl)sebacate PA0 57. di-(1-octadecyloxy-2,2,6,6-tetramethylpiperidin-4-yl)sebacate PA0 58. di-(1-nonyloxy-2,2,6,6-tetramethylpiperidin-4-yl)succinate PA0 59. di-[1-(1-methylcyclohexyloxy)-2,2,6,6-tetramethylpiperidin-4-yl]sebacate PA0 60. di-[1-(3-cyclohexen-1-yloxy)-2,2,6,6-tetramethylpiperidin-4-yl]sebacate PA0 61. di-(1-tert.butoxy-2,2,6,6-tetramethylpiperidin-4-yl)sebacate PA0 62. di-(1-carbamoyloxy-2,2,6,6-tetramethylpiperidin-4-yl)n-butylmalonate PA0 63. di-[1-(bicyclo-[4.4.0]-decyl-1-oxy)-2,2,6,6-tetramethylpiperidin-4-yl]seba cate PA0 64. di-(1-n-butylcarbamoyloxy-2,2,6,6-tetramethylpiperidin-4-yl)phthalate PA0 65. di-(1-n-butylcarbamoyloxy-2,2,6,6-tetramethylpiperidin-4-yl)n-butylmalonat e PA0 66. di-(1-phenylcarbamoyloxy-2,2,6,6-tetramethylpiperidin-4-yl)sebacate PA0 67. 4-benzoyloxy-1-benzyloxy-2,2,6,6-tetramethylpiperidine PA0 68. di-(1-octyloxy-2,2,6,6-tetramethylpiperidin-4-yl)sebacate PA0 69. N,N',N",N'"-tetrakis{2,4-bis[N-1-cyclohexyloxy-2,2,6,6-tetramethylpiperidi n-4-yl)n-butylamino]-1,3,5-triazin-6-yl}-3,3'-ethylenediiminodipropylamine PA0 70. 2,4,6-tris[N-6-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl)-n-butylami no]-1,3,5-triazine PA0 71. 2,4-bis[N-(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl)-n-butylamino ]-6-morpholino-1,3,5-triazine PA0 72. 1-octyloxy variation of compound 69 PA0 73. N,N'-bis(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl)--N,N'-bis{2,4- bis[N-(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl)-n-butylamino]1,3, 5-triazin-6-yl}hexamethylene diamine PA0 74. N,N'-bis{2,4-bis[N-(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl)-n-b utylamino]-1,3,5-triazin-6-yl}piperazine PA0 75. N-(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl) succinimide PA0 76. N-(1-methoxy-2,2,6,6-tetramethylpiperidin-4-yl) n-dodecyl succinimide PA0 77. tetrakis(1-octyloxy-2,2,6,6-tetramethylpiperidin-4-yl)-1,2,3,4-butanetetra carboxylate PA0 78. (1-methoxy-2,2,6,6-tetramethylpiperidin-4-yl)(1-octyloxy-2,2,6,6-tetrameth ylpiperidin-4-yl)sebacate.
As C.sub.7 -C.sub.9 aralkyl, R.sub.3 is particularly phenethyl or above all benzyl.
As C.sub.2 -C.sub.18 alkanoyl, R.sub.3 for example propionyl, butyryl, octanoyl, dodecanoyl, hexadecanoyl, octadecanoyl, but preferably acetyl.
If R.sub.4 is C.sub.2 -C.sub.8 alkenyl unsubstituted or substituted by a cyano, carbonyl or carbamide group, it is for example 1-propenyl, allyl, methallyl, 2-butenyl, 2-pentenyl, 2-hexenyl, 2-octenyl, 2,2-dicyanovinyl, 1-methyl-2-cyano-2-methoxycarbonyl-vinyl or 2,2-diacetylaminovinyl.
If any substituents are C.sub.2 -C.sub.12 alkylene, they are for example ethylene, propylene, 2,2-dimethylpropylene, tetramethylene, hexamethylene, octamethylene, decamethylene or dodecamethylene.
If any substituents are C.sub.6 -C.sub.15 arylene, they are for example o-, m- or p-phenylene, 1,4-naphthylene or 4,4'-diphenylene.
As C.sub.6 -C.sub.12 cycloalkylene, X is especially cyclohexylene.
The following compounds are examples of polyalkylpiperidine starting materials useful in making the hydroxylamine derivatives of formula B.
If R.sub.5 is C.sub.2 -C.sub.8 alkylene or hydroxyalkylene, it is for example ethylene, 1-methyl-ethylene, propylene, 2-ethylpropylene or 2-ethyl-2-hydroxymethylpropylene.
As C.sub.4 -C.sub.22 acyloxyalkylene, R.sub.5 is for example 2-ethyl-2-acetoxymethyl-propylene.
The following compounds are examples for polyalkylpiperidine starting materials useful in making the hydroxylamine derivatives of formula C.
If any substituents are C.sub.2 -C.sub.6 alkoxyalkyl, they are for example methoxymethyl, ethoxymethyl, propoxymethyl, tert-butoxyethyl, ethoxyethyl, ethoxypropyl, n-butoxyethyl, tert-butoxyethyl, isopropoxyethyl or propoxypropyl.
If R.sub.7 is C.sub.3 -C.sub.5 alkenyl, it is for example 1-propenyl, allyl, methallyl, 2-butenyl or 2-pentenyl.
As C.sub.7 -C.sub.9 aralkyl, R.sub.7 is in particular phenethyl or above all benzyl; and as C.sub.5 -C.sub.7 cycloalkyl, R.sub.7 is especially cyclohexyl.
If R.sub.7 is C.sub.2 -C.sub.4 hydroxyalkyl, it is for example 2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl, 2-hydroxybutyl or 4-hydroxybutyl.
As C.sub.6 -C.sub.10 aryl, R.sub.7 is in particular phenyl, or alpha- or .beta.-naphthyl which is unsubstituted or substituted by halogen or C.sub.1 -C.sub.4 alkyl.
If R.sub.7 is C.sub.2 -C.sub.12 alkylene, it is for example ethylene, propylene 2,2-dimethylpropylene, tetramethylene, hexamethylene, octamethylene, decamethylene or dodecamethylene.
If R.sub.7 is C.sub.6 -C.sub.12 arylene, it is for example o-, m- or p-phenylene, 1,4-naphthylene or 4,4'-diphenylene.
If Z' is C.sub.2 -C.sub.12 alkanoyl, it is for example propionyl, butyryl, octanoyl, dodecanoyl or preferably acetyl.
The following compounds are examples of polyalkylpiperidine starting materials useful in making hydroxylamine derivatives of formula D.
or the compounds of the following formulae: ##STR15## As C.sub.5 -C.sub.7 cycloalkyl, R.sub.8 is in particular cyclohexyl.
As C.sub.6 -C.sub.10 aryl, R.sub.8 is particularly phenyl, or alpha- or .beta.-naphthyl which is unsubstituted or substituted with halogen or C.sub.1 -C.sub.4 alkyl.
As C.sub.1 -C.sub.3 alkylene, E is for example methylene, ethylene or propylene.
As C.sub.2 -C.sub.6 alkylene, G is for example ethylene, propylene, 2,2-dimethylpropylene, tetramethylene or hexamethylene; and as C.sub.6 -C.sub.12 arylene, G is o-, m- or p-phenylene, 1,4-naphthylene or 4,4'-diphenylene.
The following compounds are examples of polyalkylpiperidine starting materials useful in making the hydroxylamine derivatives of formula E.
When the instant hydroxylamine derivative is of formula F, the following polymeric compounds are examples of starting materials useful in preparing said derivatives. ##STR16##
Additional starting hindered amine derivatives include for formula J:
For compounds of formula O, R.sub.3 is preferably C.sub.1 -C.sub.12 alkyl and C.sub.5 -C.sub.7 cycloalkyl and more preferably methyl, octyl, dodecyl and cyclohexyl.
For compounds of formula P, the following species are typical of tetracarboxylic acid dianhydrides suitable for the preparation thereof:
The following compounds are examples of hydroxylamines derivatives applicable for use in the invention:
The hydroxylamine derivatives of the instant invention are generally prepared by oxidizing the corresponding hindered amine with an appropriate peroxy compound such as hydrogen peroxide or tert-butyl hydroperoxide in the presence of a metal carbonyl or metal oxide catalyst followed by reduction of the oxyl intermediate formed to the desired N-hydroxy derivative, preferably by catalytic hydrogenation. Thereafter, the N-acyloxy derivatives are prepared by reacting the N-hydroxy hindered amine with the appropriate acid chloride, anhydride, isocyanate or substituted chloroformate. The catalytic hydrogenation can also be conducted in acetic anhydride to prepare the N-acetoxy derivative.
O-alkyl substituted N-hydroxy derivatives can be synthesized by several routes. The N-hydroxy derivative can be alkylated with sodium hydride and halogenated hydrocarbons such as benzyl bromide and ethyl iodide. N-methoxy variants can be prepared by thermolysis of a chlorobenzene solution of nitroxyl radical and di-tert-butyl peroxide. The product is formed by a coupling reaction between the nitroxyl radical and methyl radical generated from .beta.-scission of a t-butoxy radical. Other N-alkoxy variants are synthesized by coupling nitroxyl radicals with hydrocarbon radicals generated from thermal decomposition of di-tert-butyl peroxide in the presence of hydrocarbon solvents such as cyclohexane, toluene, and ethylbenzene. Significant amounts of N-methoxy HALS are also formed in most of these reactions.
A preferred approach is the preparation of N-alkoxy hindered amines directly from hindered amines. For example, a mixture of 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, aqueous t-butyl hydroperoxide, molybdenum oxide, and ethylbenzene gives a 90% yield of N-alphamethylbenzyloxy HALS. Molybdenum (VI) has been shown to increase the efficiency of both the oxidation of hindered amine to nitroxyl radical and the reaction of nitroxyl radicals with hydrocarbons. In addition, the N-hydroxy derivatives can be reacted with potassium t-butoxide and methyl acrylate to synthesize the N-alkoxy variants possessing an ester functionality.
The oxalates of formula N can be prepared by reacting (1-hydroxy-2,2,6,6-tetramethylpiperidin-4-yl)stearate, benzoate, and the like, with oxalylchloride, or for G.sub.1 being --NH--G'--NH by reacting the appropriate 1-hydroxy-2,2,6,6-tetramethyl piperidine with the appropriate diisocyanate.
The hindered amine precursors are large commercially available or can be prepared by methods known in the art.
The key aspect of the resin systems of this invention is their capability to be fully cured under ambient conditions. The applicable resin enamels and lacquers (as identified hereinabove) which can be stabilized against light, moisture and oxygen in accordance with the invention are known. For example, applicable alkyd, acrylic, polyester and epoxide resins are described in S. Paul's "Surface Coatings: Science and Technology" (1985) at pages 70-310. Various acrylic and modified acrylic resins are described in H. Kittel's "Lehrbuch der Lacke und Beschichtungen", Vol. 1. Part 2, on pages 735 and 742 (Berlin 1972), and in "Lackkunstharze" (1977), by H. Wagner and H. F. Sarx, on pages 229-238. Typical crosslinkable polyester resins which can be stabilized against the action of light and moisture are described e.g. in H. Wagner and H. F. Sarx, op. cit., on pages 86-99. The unmodified and modified alkyd resins which can be stabilized against the action of light and moisture in accordance with the invention, are the conventional resins which are used in trade sales, maintenance and automotive refinish coatings. For example, such coatings are based on alkyd resins, alkyd/acrylic resins and alkyd/silicon resins (see H. Wagner and H. F. Sarx, op. cit., pages 99-123) optionally crosslinked by isocyanates or epoxy resins.
In addition various acrylic lacquer coating compositions are disclosed in U.S. Pat. No. 4,168,249. Other acrylic/alkyd resins with polyisocyanate additives are disclosed in U.S. Pat. No. 4,471,083; and acrylic resins containing either pendant amino ester groups or glycidyl groups are described in U.S. Pat. No. 4,525,521.
The ambient cured coatings stabilized in accordance with the invention are suitable both for metal finish coatings and solid shade finishes, especially in the case of retouching finishes. The lacquers stabilized in accordance with the invention are preferably applied in the conventional manner by two methods, either by the single-coat method or by the two-coat method. In the latter method, the pigment-containing base coat is applied first and a covering coat of clear lacquer applied over it. When used in two-coat finishes, the polyalkylpiperidine derivative can be incorporated in the clear coat or both in the clear coat and in the pigmented base coat.
The amount of polyalkylpiperidine derivative employed is 0.1 to 10% by weight, based on the solvent-free binder, preferably 0.5 to 5% by weight. The binders can be dissolved or dispersed in customary organic solvents or in water or can be solvent-free.
To attain maximum light stability, the concurrent use of other conventional light stabilizers can be advantageous. Examples are UV absorbers of the benzophenone, benztriazole, acrylic acid derivative, or oxalanilide type, or aryl-s-triazines or metal-containing light stabilizers, for example organic nickel compounds. In two-coat systems, these additional light stabilizers can be added to the clear coat and/or the pigmented base coat.
If such combinations are employed, the sum of all light stabilizers is 0.2 to 20% by weight, preferably 0.5 to 5% by weight, based on the film-forming resin.
Examples of the UV absorbers which may be used in the instant compositions in conjunction with the aforementioned piperidine compounds are:
(a) 2-(2'-Hydroxyphenyl)-benzotriazoles, for example, the 5'-methyl--, 3',5'-di-tert-butyl--, 5'-tert-butyl--, 5'-(1,1,3,3-tetramethylbutyl)--, 5-chloro-3',5'-di-tert-butyl--, 5-chloro-3'-tert-butyl-5'-methyl--, 3'-sec-butyl-5'-tert-butyl--, 4'-octoxy--, 3',5'-di-tert-amyl derivative.
(b) 2-Hydroxy-benzophenones, for example, the 4-hydroxy--, 4-methoxy--, 4-octoxy--, 4-decyloxy--, 4-dodecyloxy--, 4-benzyloxy, 4,2',4'-trihydroxy- and 2'-hydroxy-4,4'-dimethoxy derivative.
(c) Acrylates, for example, alpha-cyano-.beta.,.beta.-diphenylacrylic acid ethyl ester or isoctyl ester, alpha-carbomethoxy-cinnamic acid methyl ester, alpha-cyano-.beta.-methyl-p-methoxy-cinnamic acid methyl ester or butyl ester, alpha-carbomethoxy-p-methoxy-cinnamic acid methyl ester, N-(.beta.-carbomethoxy-.beta.-cyanovinyl)-2-methyl-indoline.
(d) Nickel compounds, for example, nickel complexes of 2,2'-thiobis-[4-(1,1,3,3-tetramethylbutyl)-phenol], such as the 1:1 or 1:2 complex, optionally with additional ligands such as n-butylamine, triethanolamine or N-cyclohexyl-diethanolamine, nickel dibutyldithiocarbamate, nickel salts of 4-hydroxy-3,5-di-tert-butylbenzylphosphonic acid monoalkyl esters, such as of the methyl, ethyl or butyl ester, nickel complexes of ketoximes such as of 2-hydroxy-4-methyl-phenyl undecyl ketonoxime, nickel complexes of 4-phenyl-4-lauroyl-5-hydroxy-pyrazol, optionally with additional ligands.
(e) Oxalic acid diamides, for example, 4,4'-di-octyloxyoxanilide, 2,2'-di-octyloxy-5,5'-di-tert-butyloxanilide, 2,2'-di-dodecyloxy-5,5'-di-tert-butyl-oxanilide, 2-ethoxy-2'-ethyl-oxanilide, N,N'-bis-(3-dimethylaminopropyl)-oxalamide, 2-ethoxy-5-tert-butyl-2'-ethyloxanilide and its mixture with 2-ethoxy-2'-ethyl-5,4'-di-tert-butyloxanilide and its mixtures of ortho- and paramethoxy- as well as of o- and p-ethoxy-disubstituted oxanilides.
(f) Hydroxyphenyl-5-triazines such as 2,6-bis-(2,4-di-methylphenyl)-4(2-hydroxy-4-octyloxyphenyl)-s-triaz ine or the corresponding 4(2,4-dihydroxyphenyl)derivatives.
Of particular value in the instant compositions are the benzotriazoles of high molecular weight and low volatility such as 2-[2-hydroxy-3,5-di(alpha,alpha-dimethylbenzyl)-phenyl]-2H-benzotriazole, 2-(2-hydroxy-3,5-di-tert-octylphenyl)-2H-benzotriazole, 2-(2-hydroxy-3-alpha,alpha-dimethylbenzyl-5-tert-octyl-phenyl)-2H-benzotri azole, 2-(2-hydroxy-3-tert-octyl-5-alpha,alpha-di-methylbenzylphenyl)-2H-benzotri azole, 2-(2-hydroxy-3,5-di-tert-amylphenyl)-2H-benzotriazole, 2-[2-hydroxy-3-tert-butyl-5-(2-omega-hydroxy-octa-(ethyleneoxy)carbonyl)-e thylphenyl]-2H-benzotriazole, dodecylated 2-[2-hydroxy-5-methylphenyl)-2H-benzotriazole, 2-[2-hydroxy-3-tert.butyl-5-(2-octyloxycarbonyl)-ethylphenyl]-2H-benzotria zole and the 5-chloro compounds corresponding to each of the above named benzotriazoles.
Most preferably the benzotriazoles useful in the instant compositions are 2-[2-hydroxy-3,5-di(alpha,alpha-dimethylbenzyl)phenyl]-2H-benzotriazole, dodecylated 2-[2-hydroxy-5-methylphenyl)-2H-benzotriazole, 2-[2-hydroxy-3-tert-butyl-5-(2-(omega-hydroxy-octa-(ethyleneoxy)carbonyl)e thylphenyl]-2H-benzotriazole, 2-[2-hydroxy-3-tert.-butyl-5-(2-octyloxycarbonyl)-ethylphenyl]-2H-benzotri azole and 5-chloro-2-[2-hydroxy-3-tert.butyl-5-(2-octyloxycarbonyl)ethylphenyl]-2H-b enzotriazole.
A preferred embodiment of the instant invention pertains to stabilized compositions comprising
(a) a resin system as defined hereinabove, PA1 (b) a NOR.sub.1 -substituted 2,2,6,6-tetraalkylpiperidine compound, and PA1 (c) a UV absorber selected from the group consisting of the benzophenones, benzotriazoles, acrylic acid derivatives, organic nickel compounds, aryl-s-triazines and oxanilides.
Further ingredients which the enamels or coatings can contain are antioxidants, for example those of the sterically hindered phenol derivative type, phosphorus compounds, such as phosphites, phosphines or phosphonites, conventional hindered amine light stabilizers, plasticizers, levelling assistants, hardening catalysts, thickeners, dispersants or adhesion promoters.
A further preferred embodiment of the instant invention is a stabilized composition containing components (a), (b) and (c) described above which additionally contains as component (d) a phosphite or phosphonite.
The amount of phosphite or phosphonite d) which is used in the instant compositions is from 0.05 to 2% by weight, preferably from 0.1 to 1% by weight, based on the film forming resin. In two-coat systems, these stabilizers may be added to the clear coat and/or the base coat.
Typical phosphite and phosphonites include triphenyl phosphite, diphenylalkyl phosphites, phenyldialkyl phosphites, tri-(nonylphenyl)phosphite, trilauryl phosphite, trioctadecyl phosphite, di-stearyl-pentaerythritol diphosphite, tris-(2,4-di-tert.butylphenyl) phosphite, di-isodecylpentaerythritol diphosphite, di-(2,4-di-tert.butylphenyl)pentaerythritol diphosphite, tristearyl-sorbitol triphosphite, tetrakis-(2,4-di-tert.butylphenyl)-4,4'-diphenylylenediphosphonite.
The stabilizers are needed to impart greater retention of durability to the ambient cured enamels (as measured by 20.degree. gloss, distinction of image, cracking or chalking); the enamel should not yellow on curing and further color change on exposure to light should be minimized; the stabilizers should be soluble in the organic solvents normally used in coating applications such as methyl amyl ketone, xylene, n-hexyl acetate, alcohol and the like.
The instant hindered amine light stabilizers substituted on the hindered N-atom by an 0-substituted moiety fulfill each of these requirements and provide individually or in combination with a UV-absorber outstanding light stabilization protection to the ambient cured coatings.